In connection with the enhancement of processing ability in computers, the development/spread of mobile devices, and the advent of broadband era where these devices are connected with each other via communication lines to exchange massive data therebetween, the amount of communication/processing data has been drastically increased. Collaterally, memory capacity in recent recording media for storing such massive data has been remarkably increased. At present, the memory capacity of a recording medium is increased up to several to over ten gigabits for MOs, DVDs or optical disks, and 16 to 256 gigabits for DRAMs.
The need for higher capacity in these recording media is becoming higher along with the popularization of image data processing and other factors, and various concept/practical developments are being made to break through limitations in not only removable type recording media, such as optical disks, but also randomly accessible memories, such as DRAMs, for an internal memory of a computer, so as to increase their storage capacity.
Magnetic recording media, which are writable/computer-readable and highly reliable, are widely used as embedded-type recording devices, such as computer hard disks. The magnetic recording media have a high storage capacity, which is currently increased up to several ten gigabits per square inch.
While there is the same strong need for higher storage capacity in magnetic recording media, the storage capacity of the magnetic recording medium based on a conventional recording system, or a longitudinal magnetic recording system designed to magnetize a magnetic film in a direction parallel to the film, is already close to its ultimate value, because the size of magnetic particles and the thickness of a magnetic film, which are inevitably reduced in connection with the increase in storage capacity, lead to decrease in anisotropic energy for magnetizing these magnetic particles and particle energy dependent on particle volume, and the resulting influence of thermal energy undesirably induces so-called thermal fluctuation phenomenon where magnetically recorded data, or magnetic record, will disappear over time.
A perpendicular magnetic recording system proposed by Emeritus Professor Shunichi Iwasaki, Tohoku University, Japan, in 1977, is intended to magnetize a magnetic recording film in a direction perpendicular to the film, and expected to be a technology allowing a drastic increase in storage capacity, because this system has a potential for bringing about effects of providing recording-magnetization enhanced by a diamagnetic field from adjacent bits while maintaining the thickness of the film to reduce the adverse affect of thermal fluctuation.
However, any magnetic-record writing mechanism suitable for this system has not been developed. This system also involves a certain restriction in access method due to the necessity of providing a drive mechanism for a recording medium as in the conventional recoding media, which causes difficulties in increasing a writing/reading speed.
Specifically, even though computer internal memories requiring a drive mechanism, such as a magnetic disk, MO or DVD, are randomly accessible, they are short on access speed due to mechanical motion going along with an access operation. Moreover, a mobile device involves difficulties in assuring a space for incorporating a drive mechanism for recording media, and thus cannot employ such recording media advanced in terms of higher storage capacity.
Thus, as challenges for the future, it is desired to achieve the writing/reading of a magnetic record to a magnetic film based on the perpendicular magnetic recording system so as to provide high-capacity recording media, and to eliminate the use of any mechanical drive mechanism so as to achieve purely-electrical random access with an extremely high writing/reading speed.